1. Field of the Invention
The present invention relates to a method of chemically changing the physical state of hazardous waste contaminants found in an organic matrix. In particular, it relates to chemical bonding and microencapsulation of contaminants found in an organic matrix so that the contaminants are either immobilized or are partially immobilized in a homogeneous solid mass.
2. Background of the Prior Art
The disposal of hazardous wastes using a pozzolanic material has been attempted for many years. Solidification of inorganic hazardous waste found in the form of liquids, slurries, sludges and other forms of non-solids has been previously found to be possible by mixing the inorganic waste streams with a cementitious material such as Portland cement, fly ash, kiln dust, lime or a combination of these pozzolanic materials. A typical mixture could contain one part waste to two parts or more of cementitious material. The relative proportions of cementitious material added to the inorganic fluid is normally determined by the moisture content of the fluid as well as the percentage of suspended soils found in the fluid. If the inorganic hazardous waste is very aqueous, normally a great deal of cementitious material is required to eliminate the moisture. This usually results in a significant increase in volume of the waste after treatment.
It has also been known in the past that certain additives can be employed to accelerate the setting time and hardening of the inorganic fluid hazardous waste mixed with one or more combinations of the cementitious materials. Some of the more common accelerators used are calcium chloride, sodium carbonate, sodium silicate, sodium metasilicate, sodium hydroxide, and triethanolamine. It is also known that these accelerators are proportionately employed at levels from 5% to 10% based upon the dry weight of the cementitious material.
In the past, various attempts have been made to adapt the technology for solidification of inorganic hazardous waste to solidify hazardous waste contaminants in an organic matrix. An organic waste matrix is defined as a waste blend having carbon molecules present. Even when massive, proportionate amounts of pure Portland cement is mixed with organic-bearing waste to solidify the waste, batches of the organic waste remains in a plastic state and will not solidify.
Research in the past indicates that organic compounds act as an interference mechanism in the cementing process and inhibit the chemical reaction sufficiently to cause set retardation. There is little in the literature dealing with the set retardation phenomena of organics, and even less concerning the chemical or physical ability to overcome the retarding phenomena.
J.H. Taplin in 1962, Taplin, J.F., 1962, Discussion of paper by H.E. Vivian, Fourth Intern. Symp. Chemistry of Cements, Wash. D.C., U.S. National Bureau of Stds. Monogr. 43, Vol. II, p. 924, and later B. Blank, et. al., in 1963, Blank, B., D.R. Rossington, and L.A. Weinland, 1963, "Adsorption of Admixture on Portland Cement," American Ceramics Society, Vol. 46, p. 395., Brussels, Bldg. Res. Station (England), Paper 61, 68, introduced research findings that supported the retardation effects of organics with regard to a layering effect surrounding particles of cementitious material that blocked release of energies. They both postulated that the retarding organic effect is related to adsorption of organic molecules by crystalline particles. This strong adsorption and thick layering is generated by calcium sulfoaluminate hydrates resulting from the hydration of calcium hydroxide and calcium sulphate.
Calcium chloride has long been recognized within the cement industry as one of the most common accelerators used to speed up concrete setting times. Also, for example, U.S. Pat. No.4,240,952 issued to Hulbert et. al., stated that calcium chloride can be used to break the sulfo-aluminate layer encapsulating the cementitious particles. Hulbert stated that the addition of calcium chloride, to the extent of 3% by weight of the fly ash used, removes the sulfo-aluminate layer which inhibits hydration of the mixture.
When moisture is added to fly ash, chemical reactions proceed rapidly and are described by William C. Webster, in U.S. Pat. No. 4,354,876, as reactions"... resembling the flash set characteristics of improperly calcined or regulated Portland cement." As further stated by Webster, this flash set phenomena is prevalent in fly ash residue created by burning subbituminous and lignite coal. Because of the rapid flash set characteristic, much of the energy that could be released, if time permitted, is trapped. Additionally, as hydration occurs, the sulpho-aluminate layering effect occurs as well, which further adds to the encapsulating effect and blocks full release of the cementing energies. Bituminous fly ashes do not have the higher concentrations of calcium oxide and calcium sulfate, hence they will not harden rapidly when moisture is introduced.
In 1967, M.H. Roberts, M.H., 1967, "Effect of admixtures on the Composition of the Liquid Phase and the Early Hydration Reactions in Portland Cement Pastes, "Rilem Symposium on Admixtures for Mortar and Concrete, demonstrated that the addition of sucrose increases the concentration of calcium and alumina in solution to above normal levels. Further work by J.F. Young in 1972, Young, J.F., 1970, J. Amer. Ceram. Soc., V. 53, p. 65, Young, J.F., (1972), A Review of the Mechanisms of SetRetardation in Portland Cement Pastes Containing Organic Admixtures, Cement Concr. Res., Vol. 2, pp. 415-433, revealed that the formation of tricalcium aluminate, one of the key crystalline structures of fly ash cementing, is enhanced by additions of other sugar compounds such as succinic acid and tartaric acid in addition to sucrose. The work of both Roberts and Young demonstrate the ability to use sugar compounds to enhance crystalline development by keeping the key cementitious materials in suspension for greater periods of time.
The prior art does not teach an effective method of solidifying and immobilizing organic wastes in a homogeneous solid. It is the object of the present invention to teach a combination of components that, if used in the presence of Portland cement or fly ash, solidify and immobilize or partially immobilize various hazardous waste contaminants found in an organic matrix.
It is a further object of the present invention to teach a method for solidifying and completely or partially immobilizing various hazardous waste contaminants which are found in an organic matrix.